While there were some radio frequency navigation systems like LORAN and Gee, these are nearly all gone in favor of GPS. Ham radio operators are still there, of course, as are some time and frequency standard stations like WWV. Perhaps the biggest commercial users of the radio bands now are transoceanic aviation and ships at sea, but even then, many of those uses are now using satellites and much higher frequencies. Sure, that uses radio, but not ionosphere propagation. Many people listen to FM (which propagates differently), satellite radio, or they stream audio from the Internet. Even the AM radio band isn’t the mainstay it used to be.
Broadcasters that want to reach an international audience use the Internet to do that now unless they are targeting a part of the world where Internet is rare or restricted. If you own a shortwave radio, you may have noticed there isn’t as much to listen to broadcast-wise as there was decades ago. Today, it might not matter nearly as much. In the 1700s, who would care? In the mid 20th century, though, lots of things relied on this property of high-frequency radio waves. The effects are mostly related to the propagation of radio waves via the ionosphere. The X-ray and UV radiation travel at the same speed as light, so by the time we see a flare, it is too late to do anything about it, even if we could. In October, AR2775 set off two C flares and while plasma from the flare didn’t hit Earth, UV radiation caused a brief radio outage over South America. This happens more often than you might think. That led us to ask ourselves: What if there were a major radio disruption? The sunspot in question is facing Earth for the moment, so any new flares will cause more problems. NOAA also has a scale for radio disruptions ranging from R1 (an M1 flare) to R5 (an X20 flare).
You might not have noticed, but if you lived in Australia or around the Indian Ocean and you were using radio frequencies below 10 MHz, you would have noticed since the flare caused a 20-minute-long radio blackout at those frequencies.Īccording to NOAA’s Space Weather Prediction Center, the sunspot has the energy to produce M-class flares which are an order of magnitude more powerful. So a C5 is just about dead center of the scale. Flares range from A, B, C, M, and X with a zero to nine scale in each category (or even higher for giant X flares). Well, that’s a bit dramatic (it explodes a lot) - but a particularly large sunspot named AR2781 produced a C5-class solar flare which is a medium-sized explosion even for the Sun.